Dielectric gap-filling process for semiconductor device

ABSTRACT

A semiconductor device and a method of forming the same are provided. The method includes forming a trench in a substrate. A liner layer is formed along sidewalls and a bottom of the trench. A silicon-rich layer is formed over the liner layer. Forming the silicon-rich layer includes flowing a first silicon precursor into a process chamber for a first time interval, and flowing a second silicon precursor and a first oxygen precursor into the process chamber for a second time interval. The second time interval is different from the first time interval. The method further includes forming a dielectric layer over the silicon-rich layer.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications,such as, for example, personal computers, cell phones, digital cameras,and other electronic equipment. Semiconductor devices are typicallyfabricated by sequentially depositing insulating or dielectric layers,conductive layers, and semiconductor layers of material over asemiconductor substrate, and patterning the various material layersusing lithography to form circuit components and elements thereon.

The semiconductor industry continues to improve the integration densityof various electronic components (e.g., transistors, diodes, resistors,capacitors, etc.) by continual reductions in minimum feature size, whichallow more components to be integrated into a given area. However, asthe minimum features sizes are reduced, additional problems arise thatshould be addressed.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a perspective view of a fin field-effect transistor (“FinFET”)device in accordance with some embodiments.

FIGS. 2A-6A are cross-sectional views of intermediate stages in themanufacture of a FinFET device in accordance with some embodiments.

FIG. 7 is a flow diagram illustrating a dielectric gap-filling processin accordance with some embodiments.

FIG. 8 is a flow diagram illustrating a dielectric gap-filling processin accordance with some embodiments.

FIG. 9 is a flow diagram illustrating a dielectric gap-filling processin accordance with some embodiments.

FIG. 10 is a flow diagram illustrating a dielectric gap-filling processin accordance with some embodiments.

FIG. 11 illustrates structural formulas of precursors in accordance withsome embodiments.

FIGS. 12A and 13A are cross-sectional views of intermediate stages inthe manufacture of a FinFET device in accordance with some embodiments.

FIGS. 14A and 14B are cross-sectional views of an intermediate stage inthe manufacture of a FinFET device in accordance with some embodiments.

FIGS. 15A, 15B and 15C are cross-sectional views of an intermediatestage in the manufacture of a FinFET device in accordance with someembodiments.

FIGS. 16A, 16B and 16C are cross-sectional views of an intermediatestage in the manufacture of a FinFET device in accordance with someembodiments.

FIGS. 17A, 17B and 17C are cross-sectional views of an intermediatestage in the manufacture of a FinFET device in accordance with someembodiments.

FIGS. 18A, 18B and 18C are cross-sectional views of an intermediatestage in the manufacture of a FinFET device in accordance with someembodiments.

FIGS. 19A, 19B and 19C are cross-sectional views of an intermediatestage in the manufacture of a FinFET device in accordance with someembodiments.

FIG. 20C is a cross-sectional view of an intermediate stage in themanufacture of a FinFET device in accordance with some embodiments.

FIGS. 21A, 21B and 21C are cross-sectional views of an intermediatestage in the manufacture of a FinFET device in accordance with someembodiments.

FIGS. 22A, 22B and 22C are cross-sectional views of an intermediatestage in the manufacture of a FinFET device in accordance with someembodiments.

FIGS. 23A, 23B and 23C are cross-sectional views of an intermediatestage in the manufacture of a FinFET device in accordance with someembodiments.

FIGS. 24A, 24B and 24C are cross-sectional views of an intermediatestage in the manufacture of a FinFET device in accordance with someembodiments.

FIGS. 25A, 25B and 25C are cross-sectional views of an intermediatestage in the manufacture of a FinFET device in accordance with someembodiments.

FIGS. 26A, 26B and 26C are cross-sectional views of a FinFET device inaccordance with some embodiments.

FIGS. 27A, 27B and 27C are cross-sectional views of a FinFET device inaccordance with some embodiments.

FIG. 28 is a flow diagram illustrating a method of forming a FinFETdevice in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Embodiments will be described with respect to a specific context,namely, a dielectric gap-filling process for a semiconductor device. Insome embodiments, the dielectric gap-filling process may be used to formisolation regions of a semiconductor device. In other embodiments, thedielectric gap-filling process may be used to form an interlayerdielectric layer over a semiconductor device. In some embodiments, thedielectric gap-filling process includes forming a precursor soak layerin a trench or a recess before filing the trench or the recess with adielectric material. In other embodiments, the dielectric gap-fillingprocess further includes performing an ultraviolet/oxygen treatmentfollowed by a thermal treatment. Various embodiments presented hereinallow for forming dielectric layers having improved film quality nearseam regions of the dielectric layers and allow for reducing or avoidingoxidation of a substrate. Various embodiments further allow for avoidinghigh temperature and lengthy anneal process and, consequently, improvinga wafer-per-hour (WPH) yield and reducing production cost. Variousembodiments presented herein are discussed in the context of a FinFETdevice formed using a gate-last process. In other embodiments, agate-first process may be used. Also, some embodiments contemplateaspects used in planar transistor devices, multiple-gate transistordevices, 2D transistor devices, gate-all-around transistor devices,nanowire transistor devices, or the like.

FIG. 1 illustrates an example of a fin field-effect transistor (FinFET)device 100 in a three-dimensional view. The FinFET device 100 comprisesa fin 105 on a substrate 101. The substrate 101 includes isolationregions 103, and the fin 105 protrudes above and from betweenneighboring isolation regions 103. A gate dielectric 107 is alongsidewalls and over a top surface of the fin 105, and a gate electrode109 is over the gate dielectric 107. Source/drain regions 111 and 113are disposed in opposite sides of the fin 105 with respect to the gatedielectric 107 and gate electrode 109. The FinFET device 100 illustratedin FIG. 1 is provided for illustrative purposes only and is not meant tolimit the scope of the present disclosure. As such, many variations arepossible, such as epitaxial source/drain regions, multiple fins,multilayer fins, etc.

FIGS. 2A-6A, 12A-19A, 21A-25A, 14B-19B, 21B-25B, and 15C-25C arecross-sectional views of intermediate stages in the manufacturing of aFinFET device 200 in accordance with some embodiments. In FIGS. 2A-6A,12A-19A, 21A-25A, 14B-19B, 21B-25B, and 15C-25C, figures ending with an“A” designation are illustrated along the reference cross-section A-Ashown in FIG. 1, except for multiple FinFETs and multiple fins perFinFET; figures ending with a “B” designation are illustrated along thereference cross-section B-B shown in FIG. 1; and figures ending with a“C” designation are illustrated along the cross-section C-C shown inFIG. 1.

FIG. 2A illustrates a substrate 201. The substrate 201 may be asemiconductor substrate, such as a bulk semiconductor, asemiconductor-on-insulator (SOI) substrate, or the like, which may bedoped (e.g., with a p-type or an n-type dopant) or undoped. Thesubstrate 201 may be a wafer, such as a silicon wafer. Generally, an SOIsubstrate comprises a layer of a semiconductor material formed on aninsulator layer. The insulator layer may be, for example, a buried oxide(BOX) layer, a silicon oxide layer, or the like. The insulator layer isprovided on a substrate, typically a silicon or glass substrate. Othersubstrates, such as a multi-layered or gradient substrate may also beused. In some embodiments, the semiconductor material of the substrate201 may include silicon; germanium; a compound semiconductor includingsilicon carbide, gallium arsenic, gallium phosphide, indium phosphide,indium arsenide, and/or indium antimonide; an alloy semiconductorincluding SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP;combinations thereof; or the like.

The substrate 201 may further include integrated circuit devices (notshown). As one of ordinary skill in the art will recognize, a widevariety of integrated circuit devices such as transistors, diodes,capacitors, resistors, the like, or combinations thereof may be formedin and/or on the substrate 201 to generate the structural and functionalrequirements of the design for the FinFET device 200. The integratedcircuit devices may be formed using any suitable methods.

In some embodiments, appropriate wells (not shown) may be formed in thesubstrate 201. In some embodiments where the FinFET device 200 is ann-type device, the wells are p-wells. In some embodiments where theFinFET device 200 is a p-type device, the wells are n-wells. In otherembodiments, both p-wells and n-wells are formed in the substrate 201.In some embodiments, p-type impurities are implanted into the substrate201 to form the p-wells. The p-type impurities may be boron, BF₂, or thelike, and may be implanted to a concentration in a range from about 10¹⁷cm⁻³ to about 10²² cm⁻³. In some embodiments, n-type impurities areimplanted into the substrate 201 to form the n-wells. The n-typeimpurities may be phosphorus, arsenic, or the like, and may be implantedto a concentration in a range from about 10¹⁷ cm⁻³ to about 10¹⁸ cm⁻³.After implanting the appropriate impurities, an annealing process may beperformed on the substrate to activate the p-type and n-type impuritiesthat were implanted.

FIG. 2A further illustrates the formation of a mask 203 over thesubstrate 201. In some embodiments, the mask 203 may be used in asubsequent etching step to pattern the substrate 201 (see FIG. 3A). Insome embodiments, the mask 203 may comprise one or more mask layers. Asshown in FIG. 2A, in some embodiments, the mask 203 may include a firstmask layer 203A and a second mask layer 203B over the first mask layer203A. The first mask layer 203A may be a hard mask layer, may comprisesilicon oxide, silicon nitride, silicon oxynitride, silicon carbide,silicon carbonitride, a combination thereof, or the like, and may beformed using any suitable process, such as thermal oxidation, thermalnitridation, atomic layer deposition (ALD), physical vapor deposition(PVD), chemical vapor deposition (CVD), a combination thereof, or thelike. The first mask layer 203A may be used to prevent or minimizeetching of the substrate 201 underlying the first mask layer 203A in thesubsequent etching step (see FIG. 3A). The second mask layer 203B maycomprise a photoresist, and in some embodiments, may be used to patternthe first mask layer 203A for use in the subsequent etching step. Thesecond mask layer 203B may be formed using a spin-on technique and maybe patterned using acceptable photolithography techniques. In someembodiments, the mask 203 may comprise three or more mask layers.

FIG. 3A illustrates the formation of semiconductor strips 303 in thesubstrate 201. First, the mask layers 203A and 203B are patterned, whereopenings in mask layers 203A and 203B expose areas of the substrate 201where trenches 301 will be formed. Next, an etching process isperformed, where the etching process creates the trenches 301 in thesubstrate 201 through the openings in the mask 203. The remainingportions of the substrate 201 underlying a patterned mask 203 form aplurality of semiconductor strips 303. The etching may be any acceptableetch process, such as a reactive ion etch (RIE), neutral beam etch(NBE), a combination thereof, or the like. The etch process may beanisotropic. In some embodiments, after forming the semiconductor strips303, any remaining portions of the mask 203 may be removed by anysuitable process. In other embodiments, portions of the mask 203, suchas the first mask layer 203A, may remain over the semiconductor strips303. In some embodiments, the semiconductor strips 303 may have a heightH₁ between about 45 nm and about 55 nm. In some embodiments, thesemiconductor strips 303 may have a width W₁ between about 5 nm andabout 10 nm.

FIGS. 4A-6A illustrate a dielectric gap-filling process for forming oneor more dialectic materials in the trenches 301. FIG. 4A illustrates theformation of a conformal liner layer 401 on sidewalls and bottomsurfaces of the trenches 301. FIG. 5A illustrates the formation of aprecursor soak layer 501 over the liner layer 401. FIG. 6A illustratedthe formation of a dielectric layer 601 in the trenches 301. The detailsof the dielectric gap-filling process are provided below with referenceto FIGS. 7-11.

FIG. 7 is a flow diagram illustrating a dielectric gap-filling process700 in accordance with some embodiments. Referring to FIGS. 4A and 7, instep 701, the liner layer 401 is formed on the sidewalls and the bottomsurfaces of the trenches 301. In some embodiments, the liner layer 401may comprise a semiconductor (e.g., silicon) nitride, a semiconductor(e.g., silicon) oxide, a thermal semiconductor (e.g., silicon) oxide, asemiconductor (e.g., silicon) oxynitride, a polymer, combinationsthereof, or the like. The formation of the liner layer 401 may includeany suitable method, such as ALD, CVD, high density plasma chemicalvapor deposition (HDP-CVD), PVD, a combination thereof, or the like. Inan embodiment where the liner layer 401 comprises silicon nitride, theliner layer 401 is formed by an ALD process using a precursor such asDCS (SiCl₂H₂), a silicon tetrachloride, a combination thereof, or thelike. In an embodiment where the liner layer 401 comprises siliconoxide, the liner layer 401 is formed by an ALD process using a precursorsuch as LTO520, SAM24, 3DMAS, a combination thereof, or the like. Insome embodiments, the liner layer 401 has a thickness between about 20 Åand about 40 Å, such as about 20 Å.

Referring to FIGS. 5A and 7, in step 703, the precursor soak layer 501is formed over the liner layer 401. In some embodiments, the precursorsoak layer 501 may comprise an oxide, such as silicon oxide, or thelike. The formation of the precursor soak layer 501 may include anysuitable method, such as ALD, CVD, HDP-CVD, a combination thereof, orthe like. In some embodiments wherein the precursor soak layer 501comprises silicon oxide formed using ALD, the formation of the precursorsoak layer 501 may comprise steps 707 and 709. In some embodiments, thesubstrate 201 comprising the structure of FIG. 4A is placed on a supportstructure (such as, for example, a chuck) within a process chamber. Thesupport structure may be configured to rotate the substrate 201 duringthe formation of the precursor soak layer 501, where one full rotationof the substrate 201 is one cycle of the deposition process. In someembodiments, each cycle has a duration between about 6 sec and about 60sec.

In step 707, after placing the substrate 201 within the process chamber,a first silicon precursor is flown into the process chamber. The firstsilicon precursor may include LTO520, SAM24, 3DMAS, a combinationthereof, or the like. FIG. 11 illustrates a structural formula 1101 ofLTO520, where R may comprise C₁-C₅ alkyl, C₂-C₅ alkenyl, C₂-C₂₀ alkynyl,or the like. FIG. 11 further illustrates a structural formula 1103 of3DMAS and a structural formula 1105 of SAM24. In some embodiments, thefirst silicon precursor is flown into the process chamber for N1 cycles.In some embodiments, the first silicon precursor has a flow rate betweenabout 50 sccm and about 100 sccm. In some embodiments, the first siliconprecursor is flown into the process chamber for a duration between about60 sec and about 90 sec. In some embodiments, N1 is between 1 and 5,such as 5.

In step 709, a second silicon precursor and a first oxygen precursor maybe flown into the process chamber for N2 cycles. The second siliconprecursor may be chosen from same candidate chemicals as the firstsilicon precursor described above with respect to step 707, and thedescription is not repeated herein. In some embodiments, the firstsilicon precursor and the second silicon precursor may comprise a samechemical. In other embodiments, the first silicon precursor and thesecond silicon precursor may comprise different chemicals. In someembodiments, the first oxygen precursor may include O₂, O₃, acombination thereof, or the like. In some embodiments where the firstoxygen precursor is O₃, the first oxygen precursor may have a densitybetween about 50 g/m³ and about 400 g/m³, such as about 300 g/m³. Insome embodiments, the second silicon precursor has a flow rate betweenabout 10 sccm and about 300 sccm. In some embodiments, the first oxygenprecursor has a flow rate between about 10 sccm and about 100 sccm. Insome embodiments, the second silicon precursor and the first oxygenprecursor are flown into the process chamber for a duration betweenabout 6 sec and about 120 sec. In some embodiments, N2 is between 1 and20, such as 5. In some embodiments, N2 may be different from N1.

In some embodiments, the cycle numbers N1 and N2 may be varied to adjustsilicon content in the precursor soak layer 501. In some embodiments,the precursor soak layer 501 is a silicon-rich layer having siliconcontent of between about 30 atomic % and about 40 atomic %. In someembodiments, the cycle numbers N1 and N2 may be further varied to adjusta thickness of the precursor soak layer 501. In some embodiments, theprecursor soak layer 501 may have a thickness between about 3 Å andabout 5 Å.

Referring to FIGS. 6A and 7, in step 705, after forming the precursorsoak layer 501, the dielectric layer 601 is formed in the trenches 301(see FIG. 5A). The dielectric layer 601 may comprise an oxide, such assilicon oxide, a nitride, such as silicon nitride, a combinationthereof, or the like, and may be formed by ALD, CVD, HDP-CVD, flowableCVD (FCVD) (e.g., a CVD-based material deposition in a remote plasmasystem and post curing to make it convert to another material, such asan oxide), a combination thereof, or the like. Other insulationmaterials formed by any acceptable processes may be also used. In someembodiments where the dielectric layer 601 comprises silicon oxideformed using ALD, a third silicon precursor and a second oxygenprecursor is flown into the process chamber for Nd cycles. The thirdsilicon precursor may be chosen from same candidate chemicals as thefirst silicon precursor described above with respect to step 707, andthe description is not repeated herein. In some embodiments, the firstsilicon precursor, the second silicon precursor and the third siliconprecursor may comprise a same chemical. In other embodiments, the thirdsilicon precursor and at least one of the first silicon precursor andthe second silicon precursor may comprise different chemicals. Thesecond oxygen precursor may be chosen from same candidate chemicals asthe first oxygen precursor described above with respect to step 709, andthe description is not repeated herein. In some embodiments, the firstoxygen precursor and the second oxygen precursor may comprise a samechemical. In other embodiments, the first oxygen precursor and thesecond oxygen precursor may comprise different chemicals.

In some embodiments, the deposition process for forming the dielectriclayer 601 may be a plasma-assisted process or a plasma-enhanced process.In such embodiments, an oxygen-containing plasma, such as an O₂ plasma,is flown into the process chamber in addition to the third siliconprecursor and the second oxygen precursor. Radio frequency (RF) powerfor generating the oxygen-containing plasma may be between about 2 KWand about 3 KW. In some embodiments, the third silicon precursor has aflow rate between about 10 sccm and about 300 sccm. In some embodiments,the second oxygen precursor has a flow rate between about 10 sccm andabout 100 sccm. In some embodiments, the oxygen-containing plasma has aflow rate between about 10 sccm and about 100 sccm. In some embodiments,the third silicon precursor and the second oxygen precursor are flowninto the process chamber for a duration between about 6 sec and about120 sec. In some embodiments, Nd is between 1 and 20, such as 5.

Referring further to FIG. 6A, the dielectric layer 601 may comprise aseam 603 within each of the trenches 301 (see FIG. 5A) due to thedeposition process properties. In some embodiments, regions of thedielectric layer 601 near the seams 603 may be weaker than the rest ofthe dielectric layer 601. For example, the regions of the dielectriclayer 601 near the seams 603 may have a higher etch rate than the restof the dielectric layer 601 and voids may be formed near the seams 603during and/or after preforming subsequent processes on the dielectriclayer 601, such as a polishing process, an etching process, or the like.By forming the precursor soak layer 501 before forming the dielectriclayer 601, the regions of the dielectric layer 601 near the seams 603may be strengthened and formation of voids in the dielectric layer 601may be reduced or avoided. In some embodiments where the precursor soaklayer 501 and the dielectric layer 601 comprise a same material, aninterface between the precursor soak layer 501 and the dielectric layer601 may not be detectable.

FIG. 8 is a flow diagram illustrating a dielectric gap-filling process800 in accordance with some embodiments. Referring to FIGS. 4A and 8, instep 801, the liner layer 401 is formed on the sidewalls and the bottomsurfaces of the trenches 301. In some embodiments, step 801 is similarto step 701 described above with reference to FIG. 7 and the descriptionis not repeated herein.

Referring to FIGS. 5A and 8, in step 803, the precursor soak layer 501is formed over the liner layer 401. In some embodiments wherein theprecursor soak layer 501 comprises silicon oxide formed using ALD, theformation of the precursor soak layer 501 may comprise one or moredeposition loops, where each deposition loop comprises steps 807, 809,811 and 813. In some embodiments, step 803 may comprise N7 depositionloops. In some embodiments, N7 is between about 1 and bout 5. In someembodiments, the substrate 201 comprising the structure of FIG. 4A isplaced on a support structure (such as, for example, a chuck) within aprocess chamber.

In step 807, after placing the substrate 201 within the process chamber,a first silicon precursor is flown into the process chamber. The firstsilicon precursor may include LTO520, SAM24, 3DMAS, a combinationthereof, or the like. In some embodiments, the first silicon precursoris flown into the process chamber for N3 cycles. In some embodiments,the first silicon precursor has a flow rate between about 50 sccm andabout 100 sccm. In some embodiments, the first silicon precursor isflown into the process chamber for a duration between about 60 sec andabout 90 sec. In some embodiments, N3 is between 1 and 20, such as 5.

In step 809, a second silicon precursor and a first oxygen precursor maybe flown into the process chamber for N4 cycles. The second siliconprecursor may be chosen from same candidate chemicals as the firstsilicon precursor described above with respect to step 807, and thedescription is not repeated herein. In some embodiments, the firstsilicon precursor and the second silicon precursor may comprise a samechemical. In other embodiments, the first silicon precursor and thesecond silicon precursor may comprise different chemicals. In someembodiments, the first oxygen precursor may include O₂, O₃, acombination thereof, or the like. In some embodiments where the firstoxygen precursor is O₃, the first oxygen precursor may have a densitybetween about 100 g/m³ and about 300 g/m³, such as about 300 g/m³. Insome embodiments, the second silicon precursor has a flow rate betweenabout 50 sccm and about 300 sccm. In some embodiments, the first oxygenprecursor has a flow rate between about 10 sccm and about 100 sccm. Insome embodiments, the second silicon precursor and the first oxygenprecursor are flown into the process chamber for a duration betweenabout 6 sec and about 60 sec. In some embodiments, N4 is between 1 and20, such as 5. In some embodiments, N4 may be different from N3.

In step 811, a third silicon precursor is flown into the process chamberfor N5 cycles. The third silicon precursor may be chosen from samecandidate chemicals as the first silicon precursor described above withrespect to step 807, and the description is not repeated herein. In someembodiments, the first silicon precursor, the second silicon precursorand the third silicon precursor may comprise a same chemical. In otherembodiments, the third silicon precursor and at least one of the firstsilicon precursor and the second silicon precursor may comprisedifferent chemicals. In some embodiments, the third silicon precursorhas a flow rate between about 50 sccm and about 100 sccm. In someembodiments, the third silicon precursor is flown into the processchamber for a duration between about 12 sec and about 24 sec. In someembodiments, N5 is between 1 and 5, such as 2. In some embodiments, N5may be different from at least one of N3 and N4.

In step 813, a fourth silicon precursor and a second oxygen precursormay be flown into the process chamber for N6 cycles. The fourth siliconprecursor may be chosen from same candidate chemicals as the firstsilicon precursor described above with respect to step 807, and thedescription is not repeated herein. In some embodiments, the firstsilicon precursor, the second silicon precursor, the third siliconprecursor and the fourth silicon precursor may comprise a same chemical.In other embodiments, the fourth silicon precursor and at least one ofthe first silicon precursor, the second silicon precursor and the thirdsilicon precursor may comprise different chemicals. The second oxygenprecursor may be chosen from same candidate chemicals as the firstoxygen precursor described above with respect to step 809, and thedescription is not repeated herein. In some embodiments, the firstoxygen precursor and the second oxygen precursor may comprise a samechemical. In other embodiments, the first oxygen precursor and thesecond oxygen precursor may comprise different chemicals. In someembodiments where the second oxygen precursor is O₃, the second oxygenprecursor may have a density between about 100 g/m³ and about 300 g/m³,such as about 300 g/m³. In some embodiments, the fourth siliconprecursor has a flow rate between about 10 sccm and about 300 sccm. Insome embodiments, the second oxygen precursor has a flow rate betweenabout 10 sccm and about 100 sccm. In some embodiments, the fourthsilicon precursor and the second oxygen precursor are flown into theprocess chamber for a duration between about 6 sec and about 120 sec. Insome embodiments, N6 is between 1 and 5, such as 3. In some embodiments,N6 may be different from at least one of N3, N4 and N5.

In some embodiments, the cycle numbers N3, N4, N5, N6 and N7 may bevaried to adjust silicon content in the precursor soak layer 501. Insome embodiments, the precursor soak layer 501 is silicon-rich layerhaving silicon content of between about 30 atomic % and about 40 atomic%. In some embodiments, the cycle numbers N3, N4, N5, N6 and N7 may befurther varied to adjust a thickness of the precursor soak layer 501. Insome embodiments, the precursor soak layer 501 may have a thicknessbetween about 8 Å and about 12 Å. In some embodiments, the precursorsoak layer 501 formed in step 803 of the dielectric gap-filling process800 may be thicker than the precursor soak layer 501 formed in step 703of the dielectric gap-filling process 700 (see FIG. 7). By increasingthe thickness of the precursor soak layer 501, oxidation of thesubstrate 201 may be prevented or reduced.

Referring to FIGS. 6A and 8 in step 805, after forming the precursorsoak layer 501, the dielectric layer 601 is formed in the trenches 301(see FIG. 5A). In some embodiments, step 805 may be similar to step 705of the dielectric gap-filling process 700 described above with referenceto FIG. 7 and the description is not repeated herein.

FIG. 9 is a flow diagram illustrating a dielectric gap-filling process900 in accordance with some embodiments. Referring to FIGS. 9 and 6A,after performing the dielectric gap-filling process 700 illustratedabove with reference to FIG. 7, the dielectric gap-filling process 900continues to step 901, where an ultraviolet/oxygen treatment isperformed on the dielectric layer 601. In some embodiments, theultraviolet/oxygen treatment comprises subjecting the dielectric layer601 to ultraviolet (UV) radiation in an oxygen ambient. In someembodiment, an intensity of the UV radiation is between about 15 mW/cm²and about 25 mW/cm². In some embodiments, the oxygen ambient maycomprise a molecular oxygen gas (O₂), or the like. In some embodiments,the UV radiation breaks weak bonds (such as, for example, Si—H bonds)and precursor byproducts near the seams 603 of the dielectric layer 601,while the oxygen ambient provides the oxygen source to form strongerbonds (such as, for example, Si—O bonds) near the seams 603 of thedielectric layer 601.

In step 903, after performing the ultraviolet/oxygen treatment, athermal treatment is performed on the dielectric layer 601. In someembodiments, the thermal treatment may be a dry thermal treatment, a wetthermal treatment, a combination thereof, or the like. In someembodiments where the thermal treatment is a dry thermal treatment, thethermal treatment may be performed at a temperature between about 400°C. and about 700° C. for a duration between about 1 hr and about 2 hr.In some embodiments where the thermal treatment is a wet thermaltreatment, the thermal treatment may be performed at a temperaturebetween about 400° C. and about 700° C. for a duration between about 1hr and about 2 hr. Furthermore, in some embodiments where the thermaltreatment is a wet thermal treatment, the thermal treatment is performedin an ambient comprising water (H₂O) vapor. In some embodiments, thewater vapor may have a pressure between about 600 mmHg and about 1200mmHg. In some embodiments, the thermal treatment densifies thedielectric layer 601 and facilitates strong bond (such as, for example,Si—O bonds) formation at the seams 603 of the dielectric layer 601.

FIG. 10 is a flow diagram illustrating a dielectric gap-filling process1000 in accordance with some embodiments. Referring to FIGS. 10 and 6A,after performing the dielectric gap-filling process 800 illustratedabove with reference to FIG. 8, the dielectric gap-filling process 1000continues to step 1001, where an ultraviolet/oxygen treatment isperformed on the dielectric layer 601. In some embodiments, step 1001 issimilar to step 901 of the dielectric gap-filling process 900 describedabove with reference to FIG. 9 and the description is not repeatedherein. In step 1003, after performing the ultraviolet/oxygen treatment,a thermal treatment is performed on the dielectric layer 601. In someembodiments, step 1003 is similar to step 903 of the dielectricgap-filling process 900 described above with reference to FIG. 9 and thedescription is not repeated herein.

Referring to FIG. 12A, a planarization process, such as a chemicalmechanical polishing (CMP), may remove any excess portions of thedielectric layer 601, the precursor soak layer 501 and the liner layer401, such that top surfaces of the dielectric layer 601 and top surfacesof the semiconductor strips 303 are coplanar. In some embodiments whereportions of the mask 203 (see FIG. 6A) remain over the semiconductorstrips 303 after forming the semiconductor strips 303, the planarizationprocess may also remove the remaining portions of the mask 203.

FIG. 13A illustrates the recessing of the dielectric layer 601, theprecursor soak layer 501 and the liner layer 401, such that remainingportions of the dielectric layer 601, the precursor soak layer 501 andthe liner layer 401 form isolation regions 1301. The isolation regions1301 may be also referred to as shallow trench isolation (STI) regions.The dielectric layer 601, the precursor soak layer 501 and the linerlayer 401 are recessed such that fins 1303 protrude from betweenneighboring isolation regions 1301. Further, the top surfaces of theisolation regions 1301 may have a flat surface as illustrated, a convexsurface, a concave surface (such as dishing), or a combination thereof.The top surfaces of the isolation regions 1301 may be formed flat,convex, and/or concave by an appropriate etch. The dielectric layer 601,the precursor soak layer 501 and the liner layer 401 may be recessedusing one or more acceptable etching processes.

A person having ordinary skill in the art will readily understand thatthe process described with respect to FIGS. 2A-6A, 12A and 13A is justone example of how the fins 1303 may be formed. In other embodiments, adielectric layer can be formed over a top surface of the substrate 201;trenches can be etched through the dielectric layer; homoepitaxialstructures can be epitaxially grown in the trenches; and the dielectriclayer can be recessed such that the homoepitaxial structures protrudefrom the dielectric layer to form fins. In yet other embodiments,heteroepitaxial structures can be used for the fins. For example, thesemiconductor strips 303 in FIG. 12A can be recessed, and one or morematerials different from the semiconductor strips 303 may be epitaxiallygrown in their place. In even further embodiments, a dielectric layercan be formed over a top surface of the substrate 201; trenches can beetched through the dielectric layer; heteroepitaxial structures can beepitaxially grown in the trenches using one or more materials differentfrom the substrate 201; and the dielectric layer can be recessed suchthat the heteroepitaxial structures protrude from the dielectric layerto form fins 1303.

In some embodiments where homoepitaxial or heteroepitaxial structuresare epitaxially grown, the grown materials may be in situ doped duringgrowth. In other embodiments, homoepitaxial or heteroepitaxialstructures may be doped using, for example, ion implantation afterhomoepitaxial or heteroepitaxial structures are epitaxially grown. Invarious embodiments, the fins 1303 may comprise silicon germanium(Si_(x)Ge_(1-x), where x can be between approximately 0 and 1), siliconcarbide, pure or substantially pure germanium, a III-V compoundsemiconductor, a II-VI compound semiconductor, or the like. For example,the available materials for forming III-V compound semiconductorinclude, but are not limited to, InAs, AlAs, GaAs, InP, GaN, InGaAs,InAlAs, GaSb, AlSb, AlP, GaP, and the like.

Referring to FIGS. 14A and 14B, a dielectric layer 1401 is formed onsidewalls and top surfaces of the fins 1303. In some embodiments, thedielectric layer 1401 may be also formed over the isolation regions1301. In other embodiments, top surfaces of the isolation regions 1301may be free from the dielectric layer 1401. The dielectric layer 1401may comprise an oxide, such as silicon oxide, or the like, and may bedeposited (using, for example, ALD, CVD, PVD, a combination thereof, orthe like) or thermally grown (for example, using thermal oxidation, orthe like) according to acceptable techniques. A gate electrode layer1403 is formed over the dielectric layer 1401, and a mask 1405 is formedover the gate electrode layer 1403. In some embodiments, the gateelectrode layer 1403 may be deposited over the dielectric layer 1401 andthen planarized using, for example, a CMP process. The mask 1405 may bedeposited over the gate electrode layer 1403. The gate electrode layer1403 may be made of, for example, polysilicon, although other materialsthat have a high etching selectivity with respect to the material of theisolation regions 1301 may also be used. The mask 1405 may include oneor more layers of, for example, silicon oxide, silicon nitride, siliconoxynitride, silicon carbide, silicon carbonitride, a combinationthereof, or the like, and may be formed using any suitable process, suchas thermal oxidation, thermal nitridation, ALD, PVD, CVD, a combinationthereof, or the like.

Referring to FIGS. 15A, 15B, and 15C, the mask 1405 (see FIGS. 14A and14B) may be patterned using acceptable photolithography and etchingtechniques to form a patterned mask 1501. The pattern of the patternedmask 1501 is transferred to the gate electrode layer 1403 by anacceptable etching technique to form gates 1503. The gates 1503 coverrespective channel regions of the fins 1303 (see FIG. 15B) whileexposing source/drain regions of the fins 1303 (see FIGS. 15B and 15C).The gates 1503 may also have a lengthwise direction substantiallyperpendicular to the lengthwise direction of respective fins 1303,within process variations (see FIG. 15A). A size of the gates 1503, anda pitch between the gates 1503, may depend on a region of a die in whichthe gates 1503 are formed. In some embodiments, the gates 1503 may havea larger size and a larger pitch when located in, for example, aninput/output region of a die (e.g., where input/output circuitry isdisposed) than when located in, for example, a logic region of a die(e.g., where logic circuitry is disposed). As described below in greaterdetail, the gates 1503 are sacrificial gates and are subsequentlyreplaced by replacement gates. Accordingly, the gates 1503 may also bereferred to as sacrificial gates.

Referring further to FIGS. 15A, 15B, and 15C, lightly doped source/drain(LDD) regions 1505 may be formed in the substrate 201. Similar to theimplantation process discussed above with reference to FIG. 2A,appropriate impurities are implanted into the fins 1303 to form the LDDregions 1505. In some embodiments where the FinFET device 200 is ap-type device, p-type impurities are implanted into the fins 1303 toform p-type LDD regions 1505. In some embodiments where the FinFETdevice 200 is an n-type device, n-type impurities are implanted into thefins 1303 to form n-type LDD regions 1505. During the implantation ofthe LDD regions 1505, the gates 1503 and the patterned mask 1501 may actas a mask to prevent (or at least reduce) dopants from implanting intochannel regions of the fins 1303. Thus, the LDD regions 1505 may beformed substantially in source/drain regions of the fins 1303. Then-type impurities may be any of the n-type impurities previouslydiscussed, and the p-type impurities may be any of the p-type impuritiespreviously discussed. The LDD regions 1505 may have a concentration ofimpurities between about 10²⁰ cm⁻³ to about 10²¹ cm⁻³. After theimplantation process, an annealing process may be performed to activatethe implanted impurities.

FIGS. 16A-16C and 17A-17C illustrate the formation of spacers 1701 onsidewalls of the gates 1503 and sidewalls of the fins 1303 in accordancewith some embodiments. Referring first to FIGS. 16A, 16B, and 16C, adielectric layer 1601 is blanket formed on exposed surfaces of the gates1503, the patterned mask 1501, and the dielectric layer 1401. In someembodiments, the dielectric layer 1601 may comprise silicon nitride(SiN), silicon oxynitride (SiON), silicon oxycarbide (SiOC), siliconcarbonitride (SiCN), silicon carboxynitride (SiOCN), a combinationthereof, or the like, and may be formed using CVD, ALD, a combinationthereof, or the like.

Referring next to FIGS. 17A, 17B, and 17C, horizontal portions of thedielectric layer 1601 are removed, such that remaining vertical portionsof the dielectric layer 1601 form spacers 1701 on the sidewalls of thegates 1503 and the sidewalls of the fins 1303. In some embodiments, thehorizontal portions of the dielectric layer 1601 may be removed using asuitable etching process, such as an anisotropic dry etching process.

Referring to FIGS. 18A, 18B, and 18C, after forming the spacers 1701, apatterning process is performed on the fins 1303 to form recesses 1801in the source/drain regions of the fins 1303. In some embodiments, thepatterning process may include a suitable anisotropic dry etchingprocess, while using the patterned mask 1501, the gates 1503, thespacers 1701, and/or isolation regions 1301 as a combined mask. Thesuitable anisotropic dry etching process may include a reactive ion etch(RIE), a neutral beam etch (NBE), a combination thereof, or the like. Insome embodiments, portions of the dielectric layer 1401 may be removedover the isolation regions 1301 during the patterning process.

Referring to FIGS. 19A, 19B, and 19C, epitaxial source/drain regions1901 are formed in the recesses 1801 (see FIGS. 18B and 18C). In someembodiments, the epitaxial source/drain regions 1901 are epitaxiallygrown in the recesses 1801 using metal-organic CVD (MOCVD), molecularbeam epitaxy (MBE), liquid phase epitaxy (LPE), vapor phase epitaxy(VPE), selective epitaxial growth (SEG), a combination thereof, or thelike. In some embodiments where the FinFET device 200 is an n-typedevice and the fins 1303 are formed of silicon, the epitaxialsource/drain regions 1901 may include silicon, SiC, SiCP, SiP, or thelike. In some embodiments where the FinFET device 200 is a p-type deviceand the fins 1303 are formed of silicon, the epitaxial source/drainregions 1901 may include SiGe, SiGeB, Ge, GeSn, or the like. Theepitaxial source/drain regions 1901 may have surfaces raised fromrespective surfaces of the fins 1303 and may have facets. In someembodiments, the epitaxial source/drain regions 1901 may extend past thefins 1303 and into the semiconductor strips 303. In some embodiments,the material of the epitaxial source/drain regions 1901 may be implantedwith suitable dopants. In some embodiments, the implantation process issimilar to the process used for forming the LLD regions 1505 asdescribed above with reference to FIGS. 15A, 15B, and 15C, and thedescription is not repeated herein. In other embodiments, the materialof the epitaxial source/drain regions 1901 may be in situ doped duringgrowth.

Referring further to FIGS. 19A, 19B, and 19C, in the illustratedembodiment, each of the epitaxial source/drain regions 1901 arephysically separated from other epitaxial source/drain regions 1901. Inother embodiments, adjacent epitaxial source/drain regions 1901 may bemerged. Such an embodiment is depicted in FIG. 20C, where adjacentepitaxial source/drain regions 1901 are merged to form a commonepitaxial source/drain region 1901.

Referring to FIGS. 21A, 21B and 21C, a dielectric gap-filling process isperformed to fill gaps between adjacent gates 1503 and gaps betweenadjacent epitaxial source/drain regions 1901 with one or more dielectricmaterials. The dielectric gap-filling process includes forming aconformal liner layer 2101 over the gates 1503 and the epitaxialsource/drain regions 1901, forming a precursor soak layer 2103 over theliner layer 2101, and forming a dielectric layer 2105 over the precursorsoak layer 2103. In some embodiments, the liner layer 2101 may be formedusing similar materials and methods as the liner layer 401 describedabove with reference to FIG. 4A and the description is repeated herein.In some embodiments, the precursor soak layer 2103 may be formed usingsimilar materials and methods as the precursor soak layer 501 describedabove with reference to FIG. 5A and the description is repeated herein.In some embodiments, the dielectric layer 2105 is formed of a dielectricmaterial such as silicon oxide, SiOC, ZrO₂, HfO₂, Phospho-Silicate Glass(PSG), Boro-Silicate Glass (BSG), Boron-Doped Phospho-Silicate Glass(BPSG), undoped Silicate Glass (USG), low-k dielectric materials,extremely low-k dielectric materials, high-k dielectric materials, acombination thereof, or the like, and may be deposited by any suitablemethod, such as ALD, CVD, PECVD, a spin-on-glass process, a combinationthereof, or the like. The dielectric layer 2105 may also be referred toas an interlayer dielectric (ILD) layer. In some embodiments, the linerlayer 2101 is used as an etch stop layer while patterning the dielectriclayer 2105 to form openings for subsequently formed contact plugs.Accordingly, a material for the liner layer 2101 may be chosen such thatthe material of the liner layer 2101 has a lower etch rate than thematerial of the dielectric layer 2105.

In some embodiments, the dielectric gap-filling process for forming theliner layer 2101, the precursor soak layer 2103, and the dielectriclayer 2105 may comprise the dielectric gap-filling process 700 describedabove with reference to FIG. 7 and the description is not repeatedherein. In other embodiments, the dielectric gap-filling process forforming the liner layer 2101, the precursor soak layer 2103, and thedielectric layer 2105 may comprise the dielectric gap-filling process800 described above with reference to FIG. 8 and the description is notrepeated herein. In yet other embodiments, the dielectric gap-fillingprocess for forming the liner layer 2101, the precursor soak layer 2103,and the dielectric layer 2105 may comprise the dielectric gap-fillingprocess 900 described above with reference to FIG. 9 and the descriptionis not repeated herein. In yet other embodiments, the dielectricgap-filling process for forming the liner layer 2101, the precursor soaklayer 2103, and the dielectric layer 2105 may comprise the dielectricgap-filling process 1000 described above with reference to FIG. 10 andthe description is not repeated herein. In some embodiments, aplanarization process, such as a CMP process, may be performed to levelthe top surface of the dielectric layer 2105 with the top surfaces ofthe patterned mask 1501.

Referring to FIGS. 22A, 22B and 22C, the gates 1503 (see FIGS. 21A and21B) are removed to form recesses 2201. In some embodiments, the gates1503 may be removed using one or more suitable etching processes. Eachof the recesses 2201 exposes a channel region of a respective fin 1303.In some embodiments, the dielectric layer 1401 may be used as an etchstop layer when the gates 1503 are etched. In some embodiments, afterremoving the gate electrode layers 1403 of the gates 1503, exposedportions of the dielectric layer 1401 may be also removed. In someembodiments, the exposed portions of the dielectric layer 1401 mayremain in the recesses 2201.

Referring to FIGS. 23A, 23B and 23C, a gate dielectric layer 2301 and agate electrode layer 2303 are formed in the recesses 2201 (see FIGS. 22Aand 22B). In some embodiments, the gate dielectric layer 2301 isconformally deposited in the recesses 2201. In some embodiments, thegate dielectric layer 2301 comprises silicon oxide, silicon nitride, ormultilayers thereof. In other embodiments, the gate dielectric layer2301 includes a high-k dielectric material, and in these embodiments,the gate dielectric layer 2301 may have a k value greater than about7.0, and may include a metal oxide or a silicate of Hf, Al, Zr, La, Mg,Ba, Ti, Pb, and combinations thereof. The formation methods of the gatedielectric layer 2301 may include Molecular-Beam Deposition (MBD), ALD,PECVD, a combination thereof, or the like.

Referring further to 23A, 23B and 23C, in some embodiments where theportions of the dielectric layer 1401 are not removed over the channelregions of the fins 1303 while forming the recesses 2201 (see FIGS. 22Aand 22B), the portions of the dielectric layer 1401 over the channelregions of the fins 1303 may act as interfacial layers between the gatedielectric layer 2301 and the channel regions of the fins 1303. In someembodiments where the portions of the dielectric layer 1401 are removedover the channel regions of the fins 1303 while forming the recesses2201, one or more interfacial layers may be formed over the channelregions of the fins 1303 prior to forming the gate dielectric layer2301, and the gate dielectric layer 2301 is formed over the one or moreinterfacial layers. The interfacial layers help to buffer thesubsequently formed high-k dielectric layer from the underlyingsemiconductor material. In some embodiments, the interfacial layerscomprise a chemical silicon oxide, which may be formed of chemicalreactions. For example, a chemical oxide may be formed using deionizedwater+ozone (O₃), NH₄OH+H₂O₂+H₂O (APM), or other methods. Otherembodiments may utilize a different material or processes (e.g., athermal oxidation or a deposition process) for forming the interfaciallayers.

Next, the gate electrode layer 2303 is deposited over the gatedielectric layer 2301 and fills the remaining portions of the recesses2201 (see FIGS. 22A and 22B). In some embodiments, the gate electrodelayer 2303 may comprise one or more layers of suitable conductivematerials. The gate electrode layer 2303 may comprise a metal selectedfrom a group of W, Cu, Ti, Ag, Al, TiAl, TiAlN, TaC, TaCN, TaSiN, Mn,Co, Pd, Ni, Re, Ir, Ru, Pt, Zr, and combinations thereof. In someembodiments, the gate electrode layer 2303 may comprise a materialselected from a group of TiN, WN, TaN, Ru, and combinations thereof.Metal alloys such as Ti—Al, Ru—Ta, Ru—Zr, Pt—Ti, Co—Ni and Ni—Ta may beused and/or metal nitrides such as WN_(x), TiN_(x), MoN_(x), TaN_(x),and TaSi_(x)N_(y) may be used. The gate electrode layer 2303 may beformed using a suitable process such as ALD, CVD, PVD, plating,combinations thereof, or the like. After filling the recesses 2201 withthe gate electrode layer 2303, a planarization process, such as a CMPprocess, may be performed to remove the excess portions of the gatedielectric layer 2301 and the gate electrode layer 2303, which excessportions are over the top surface of the dielectric layer 2105. Theremaining portions of the gate electrode layer 2303 and the gatedielectric layer 2301 thus form replacement gates 2305 of the FinFETdevice 200. In other embodiments, the gates 1503 (see FIGS. 21A and 21B)may remain rather than being replaced by the replacement gates 2305.

Referring to FIGS. 24A, 24B and 24C, a dielectric layer 2401 is formedover the dielectric layer 2105 and the replacement gates 2305. Thedielectric layer 2401 may also be referred to as an interlayerdielectric (ILD) layer. In some embodiments, the dielectric layer 2401may be formed using similar materials and methods as the dielectriclayer 2105 described above with reference to FIGS. 21A, 21B and 21C, andthe description is not repeated herein. In some embodiments, thedielectric layer 2105 and the dielectric layer 2401 are formed of a samematerial. In other embodiments, the dielectric layer 2105 and thedielectric layer 2401 are formed of different materials. The liner layer2101, the precursor soak layer 2103, and the dielectric layers 2105 and2401 are patterned to form openings 2403 and 2405. In some embodiments,the liner layer 2101, the precursor soak layer 2103, and the dielectriclayers 2105 and 2401 may be patterned using one or more suitable etchingprocesses, such as anisotropic dry etching process, or the like. Theopenings 2403 expose the respective replacement gates 2305. The openings2405 expose portions of the respective epitaxial source/drain regions1901.

Referring further to FIGS. 24A, 24B and 24C, self-aligned silicide(salicide) layers 2407 are formed through the openings 2405. In someembodiments, a metallic material is deposited in the openings 2405. Themetallic material may comprise Ti, Co, Ni, NiCo, Pt, NiPt, Ir, PtIr, Er,Yb, Pd, Rh, Nb, a combination thereof, or the like, and may be formedusing PVD, sputtering, or the like. Subsequently, an annealing processis performed to form the salicide layers 2407. In some embodiments wherethe epitaxial source/drain regions 1901 comprise silicon, the annealingprocess causes the metallic material to react with silicon to form asilicide of the metallic material.

Referring to FIGS. 25A, 25B and 25C, contact plugs 2501 are formed inthe openings 2403 (see FIGS. 24A and 24B) and contact plug 2503 areformed in the opening 2405 (see FIGS. 24B and 24C). In some embodiments,a liner, such as a diffusion barrier layer, an adhesion layer, or thelike, and a conductive material are deposited in the openings 2403 and2405. The liner may include titanium, titanium nitride, tantalum,tantalum nitride, a combination thereof, or the like. Subsequently, theopenings 2403 and 2405 are filled with the conductive material. Theconductive material may be copper, a copper alloy, silver, gold,tungsten, aluminum, nickel, a combination thereof, or the like. Aplanarization process, such as a CMP process, may be performed to removeexcess materials from a top surface of the dielectric layer 2401. Theremaining portions of the liner and the conductive material form thecontact plugs 2501 and 2503. The contact plugs 2501 are physically andelectrically coupled to the replacement gates 2305. The contact plugs2503 are physically and electrically coupled to the epitaxialsource/drain regions 1901 through the salicide layers 2407.

FIGS. 26A, 26B and 26C are cross-sectional views of a FinFET device 2600in accordance with some embodiments. To highlight differences betweenthe FinFET device 2600 and the FinFET device 200 illustrated in FIGS.25A, 25B and 25C, the common features of these FinFET devices arelabeled by same numerical references and their description is notrepeated herein. In some embodiments, the FinFET device 2600 may beformed using a similar method as the FinFET device 200, and thedescription is not repeated herein. In the illustrated embodiment, theformation of the precursor soak layer 2103 (see FIGS. 21A, 21B, and 21C)is omitted and the dielectric layer 2105 is formed directly on the linerlayer 2101.

FIGS. 27A, 27B and 27C are cross-sectional views of a FinFET device 2700in accordance with some embodiments. To highlight differences betweenthe FinFET device 2700 and the FinFET device 200 illustrated in FIGS.25A, 25B and 25C, the common features of these FinFET devices arelabeled by same numerical references and their description is notrepeated herein. In some embodiments, the FinFET device 2700 may beformed using a similar method as the FinFET device 200, and thedescription is not repeated herein. In the illustrated embodiment, theformation of the precursor soak layer 501 (see FIG. 5A) is omitted andthe dielectric layer 601 is formed directly on the liner layer 401.

FIG. 28 is a flow diagram illustrating a method 2800 of forming a FinFETdevice in accordance with some embodiments. The method 2800 starts withstep 2801, where trenches (such as, for example, the trenches 301illustrated in FIG. 3A) are formed in a substrate (such as, for example,the substrate 201 illustrated in FIG. 3A) such that portions of thesubstrate between adjacent trenches form semiconductor strips (such as,for example, the semiconductor strips 303 illustrated in FIG. 3A) asdescribed above with reference to FIGS. 2A and 3A. In step 2803,isolation regions (such as, for example, the isolation regions 1301illustrated in FIG. 13A) are formed in the trenches such that portionsof the semiconductor strips extending above the isolation regions formthe fins (such as, for example, the fins 1303 illustrated in FIG. 13A)as described above with reference to FIGS. 4A-6A, 12A and 13. In someembodiments, step 2803 may comprise performing the dielectricgap-filling process 700 described above with reference to FIG. 7. Inother embodiments, step 2803 may comprise performing the dielectricgap-filling process 800 described above with reference to FIG. 8. In yetother embodiments, step 2803 may comprise performing the dielectricgap-filling process 900 described above with reference to FIG. 9. In yetother embodiments, step 2803 may comprise performing the dielectricgap-filling process 1000 described above with reference to FIG. 10. Instep 2805, sacrificial gates (such as, for example, the gates 1503illustrated in FIGS. 15A and 15B) are formed along sidewalls and topsurfaces of the fins as described above with reference to FIGS. 14A, 14Band 15A-15C. In step 2807, epitaxial source/drain regions (such as, forexample, the epitaxial source/drain regions 1901 illustrated in FIGS.19B and 19C) are formed in the fins as described above with reference toFIGS. 18A-18C and 19A-19C. In step 2809, a first dielectric layer (suchas, for example, the dielectric layer 2105 illustrated in FIGS. 21B and21C) is formed between adjacent sacrificial gate structures as describedabove with reference to FIGS. 21A-21C. In some embodiments, step 2809may comprise performing the dielectric gap-filling process 700 describedabove with reference to FIG. 7. In other embodiments, step 2809 maycomprise performing the dielectric gap-filling process 800 describedabove with reference to FIG. 8. In yet other embodiments, step 2809 maycomprise performing the dielectric gap-filling process 900 describedabove with reference to FIG. 9. In yet other embodiments, step 2809 maycomprise performing the dielectric gap-filling process 1000 describedabove with reference to FIG. 10. In step 2811, the sacrificial gates arereplaced with replacement gates (such as, for example, the replacementgates 2305 illustrated in FIGS. 23A and 23B) as described above withreference to FIGS. 22A-22C and 23A-23C. In step 2813, a seconddielectric layer (such as, for example, the dielectric layer 2401illustrated in FIGS. 24A-24C) is formed over the first dielectric layerand the replacement gates as described above with reference to FIGS.24A-24C. In step 2815, gate contact plugs (such as, for example, thecontact plugs 2501 illustrated in FIGS. 25A-25C) and source/gate contactplugs (such as, for example, the contact plugs 2503 illustrated in FIGS.25A-25C) are formed as described above with reference to FIGS. 24A-24Cand 25A-25C.

According to an embodiment, a method includes: forming a trench in asubstrate; forming a liner layer along sidewalls and a bottom of thetrench; forming a silicon-rich layer over the liner layer, where formingthe silicon-rich layer includes: flowing a first silicon precursor intoa process chamber for a first time interval; and flowing a secondsilicon precursor and a first oxygen precursor into the process chamberfor a second time interval, the second time interval being differentfrom the first time interval; and forming a dielectric layer over thesilicon-rich layer. In an embodiment, forming the silicon-rich layerfurther includes: flowing a third silicon precursor into the processchamber for a third time interval; and flowing a fourth siliconprecursor and a second oxygen precursor into the process chamber for afourth time interval, the fourth time interval being different from thethird time interval. In an embodiment, the first silicon precursor andthe second silicon precursor includes a same chemical. In an embodiment,the method further includes performing an ultraviolet/oxygen treatmenton the dielectric layer. In an embodiment, performing theultraviolet/oxygen treatment on the dielectric layer includes subjectingthe dielectric layer to an ultraviolet radiation in an oxygen ambient.In an embodiment, the method further includes, after preforming theultraviolet/oxygen treatment, performing a thermal treatment on thedielectric layer.

According to another embodiment, a method includes: patterning asubstrate to form trenches therein, portions of the substrate betweenadjacent trenches forming semiconductor strips; and forming isolationregions in the trenches, portions of the semiconductor strips extendingabove the isolation regions forming fins, wherein forming the isolationregions includes: conformally forming a first liner layer in thetrenches; forming a first silicon-rich layer over the first liner layer,where forming the first silicon-rich layer includes: flowing a firstsilicon precursor into a process chamber for a first number of cycles;and flowing a second silicon precursor and a first oxygen precursor intothe process chamber for a second number of cycles, the second number ofcycles being different from the first number of cycles; and forming afirst dielectric layer over the first silicon-rich layer. In anembodiment, forming the first silicon-rich layer further includes:flowing a third silicon precursor into the process chamber for a thirdnumber of cycles; and flowing a fourth silicon precursor and a secondoxygen precursor into the process chamber for a fourth number of cycles,the fourth number of cycles being different from the third number ofcycles. In an embodiment, conformally forming the first liner layer inthe trenches includes depositing a dielectric material along sidewallsand bottoms of the trenches using an atomic layer deposition (ALD)process. In an embodiment, forming the first dielectric layer includesflowing a third silicon precursor, a second oxygen precursor, and anoxygen-containing plasma into the process chamber for a third number ofcycles. In an embodiment, the method further includes: formingsacrificial gates along sidewalls and top surfaces of the fins;conformally forming a second liner layer over the sacrificial gates;forming a second silicon-rich layer over the second liner layer, whereforming the second silicon-rich layer includes: flowing a third siliconprecursor into the process chamber for a third number of cycles; andflowing a fourth silicon precursor and a second oxygen precursor intothe process chamber for a fourth number of cycles, the fourth number ofcycles being different from the third number of cycles; and forming asecond dielectric layer over the second silicon-rich layer. In anembodiment, the method further includes: performing anultraviolet/oxygen treatment on the first dielectric layer; and afterpreforming the ultraviolet/oxygen treatment, performing a thermaltreatment on the first dielectric layer. In an embodiment, performingthe ultraviolet/oxygen treatment on the first dielectric layer includessubjecting the first dielectric layer to an ultraviolet radiation in anoxygen ambient.

According to yet another embodiment, a method includes: formingisolation regions in a substrate, portion of the substrate extendingbetween and over adjacent isolation regions forming fins; formingsacrificial gates along sidewalls and top surfaces of the fins; forminga first liner layer along sidewalls and over top surfaces of thesacrificial gates; forming a first silicon-rich layer over the firstliner layer, where forming the first silicon-rich layer includes:flowing a first silicon precursor into a process chamber for a firstnumber of cycles; and flowing a second silicon precursor and a firstoxygen precursor into the process chamber for a second number of cycles,the second number of cycles being different from the first number ofcycles; and forming a first dielectric layer over the first silicon-richlayer. In an embodiment, forming the first silicon-rich layer furtherincludes: flowing a third silicon precursor into the process chamber fora third number of cycles; and flowing a fourth silicon precursor and asecond oxygen precursor into the process chamber for a fourth number ofcycles, the fourth number of cycles being different from the thirdnumber of cycles. In an embodiment, forming the isolation regionsincludes: patterning the substrate to form trenches in the substrate;conformally forming a second liner layer in the trenches; forming asecond silicon-rich layer over the second liner layer, where forming thesecond silicon-rich layer includes: flowing a third silicon precursorinto the process chamber for a third number of cycles; and flowing afourth silicon precursor and a second oxygen precursor into the processchamber for a fourth number of cycles, the fourth number of cycles beingdifferent from the third number of cycles; and forming a seconddielectric layer over the second silicon-rich layer. In an embodiment,forming the first dielectric layer includes flowing a third siliconprecursor, a second oxygen precursor, and an oxygen-containing plasmainto the process chamber for a third number of cycles. In an embodiment,the method further includes performing an ultraviolet/oxygen treatmenton the first dielectric layer. In an embodiment, the method furtherincludes, after preforming the ultraviolet/oxygen treatment, performinga thermal treatment on the first dielectric layer. In an embodiment, thefirst silicon precursor and the second silicon precursor include a samechemical.

The fins may be formed by any suitable method. For example, the fins maybe formed using one or more photolithography processes, includingdouble-patterning or multi-patterning processes. Generally,double-patterning or multi-patterning processes combine photolithographyand self-aligned processes, allowing patterns to be created that have,for example, pitches smaller than what is otherwise obtainable using asingle, direct photolithography process. For example, in one embodiment,a sacrificial layer is formed over a substrate and patterned using aphotolithography process. Spacers are formed alongside the patternedsacrificial layer using a self-aligned process. The sacrificial layer isthen removed, and the remaining spacers may then be used to pattern thefins.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method comprising: forming a trench in a substrate; forming a first liner layer along sidewalls and a bottom of the trench; forming a first silicon-rich layer over the first liner layer, silicon content of the first silicon-rich layer being between about 30 atomic % and about 40 atomic %, wherein forming the first silicon-rich layer comprises: flowing a first silicon precursor into a process chamber for a first time interval; and flowing a second silicon precursor and a first oxygen precursor into the process chamber for a second time interval, the second time interval being different from the first time interval; forming a dielectric layer over the first silicon-rich layer; forming a sacrificial gate over the substrate and the dielectric layer; forming a second liner layer along sidewalls and over a top surface of the sacrificial gate; and forming a second silicon-rich layer over the second liner layer.
 2. The method of claim 1, wherein forming the first silicon-rich layer further comprises: flowing a third silicon precursor into the process chamber for a third time interval; and flowing a fourth silicon precursor and a second oxygen precursor into the process chamber for a fourth time interval, the fourth time interval being different from the third time interval.
 3. The method of claim 1, wherein the first silicon precursor and the second silicon precursor comprise a same chemical.
 4. The method of claim 1, further comprising performing an ultraviolet/oxygen treatment on the dielectric layer.
 5. The method of claim 4, wherein performing the ultraviolet/oxygen treatment on the dielectric layer comprises subjecting the dielectric layer to an ultraviolet radiation in an oxygen ambient.
 6. The method of claim 4, further comprising, after preforming the ultraviolet/oxygen treatment, performing a thermal treatment on the dielectric layer.
 7. A method comprising: patterning a substrate to form trenches therein, portions of the substrate between adjacent trenches forming semiconductor strips; forming isolation regions in the trenches, portions of the semiconductor strips extending above the isolation regions forming fins, wherein forming the isolation regions comprises: conformally forming a first liner layer in the trenches; forming a first silicon-rich layer over the first liner layer, the first silicon-rich layer extending along sidewalls and a top surface of each of the semiconductor strips, wherein forming the first silicon-rich layer comprises: flowing a first silicon precursor into a process chamber for a first number of cycles; and flowing a second silicon precursor and a first oxygen precursor into the process chamber for a second number of cycles, the second number of cycles being different from the first number of cycles; and forming a first dielectric layer over the first silicon-rich layer; forming sacrificial gates along sidewalls and top surfaces of the fins; conformally forming a second liner layer over the sacrificial gates; forming a second silicon-rich layer over the second liner layer, wherein forming the second silicon-rich layer comprises: flowing a third silicon precursor into the process chamber for a third number of cycles; and flowing a fourth silicon precursor and a second oxygen precursor into the process chamber for a fourth number of cycles, the fourth number of cycles being different from the third number of cycles; and forming a second dielectric layer over the second silicon-rich layer.
 8. The method of claim 7, wherein forming the first silicon-rich layer further comprises: flowing a fifth silicon precursor into the process chamber for a fifth number of cycles; and flowing a sixth silicon precursor and a third oxygen precursor into the process chamber for a sixth number of cycles, the sixth number of cycles being different from the fifth number of cycles.
 9. The method of claim 7, wherein conformally forming the first liner layer in the trenches comprises depositing a dielectric material along sidewalls and bottoms of the trenches using an atomic layer deposition (ALD) process.
 10. The method of claim 7, wherein forming the first dielectric layer comprises flowing a fifth silicon precursor, a third oxygen precursor, and an oxygen-containing plasma into the process chamber for a fifth number of cycles.
 11. The method of claim 7, further comprising: performing an ultraviolet/oxygen treatment on the first dielectric layer; and after preforming the ultraviolet/oxygen treatment, performing a thermal treatment on the first dielectric layer.
 12. The method of claim 11, wherein performing the ultraviolet/oxygen treatment on the first dielectric layer comprises subjecting the first dielectric layer to an ultraviolet radiation in an oxygen ambient.
 13. The method of claim 7, wherein silicon content of the first silicon-rich layer is between about 30 atomic % and about 40 atomic %.
 14. A method comprising: forming isolation regions in a substrate, portion of the substrate extending between and over adjacent isolation regions forming fins; forming sacrificial gates along sidewalls and top surfaces of the fins; forming a first liner layer along sidewalls and over top surfaces of the sacrificial gates; forming a first silicon-rich layer over the first liner layer, wherein forming the first silicon-rich layer comprises: flowing a first silicon precursor into a process chamber for a first number of cycles; and flowing a second silicon precursor and a first oxygen precursor into the process chamber for a second number of cycles, the second number of cycles being different from the first number of cycles; and forming a first dielectric layer over the first silicon-rich layer.
 15. The method of claim 14, wherein forming the first silicon-rich layer further comprises: flowing a third silicon precursor into the process chamber for a third number of cycles; and flowing a fourth silicon precursor and a second oxygen precursor into the process chamber for a fourth number of cycles, the fourth number of cycles being different from the third number of cycles.
 16. The method of claim 14, wherein forming the isolation regions comprises: patterning the substrate to form trenches in the substrate; conformally forming a second liner layer in the trenches; forming a second silicon-rich layer over the second liner layer, wherein forming the second silicon-rich layer comprises: flowing a third silicon precursor into the process chamber for a third number of cycles; and flowing a fourth silicon precursor and a second oxygen precursor into the process chamber for a fourth number of cycles, the fourth number of cycles being different from the third number of cycles; and forming a second dielectric layer over the second silicon-rich layer.
 17. The method of claim 14, wherein forming the first dielectric layer comprises flowing a third silicon precursor, a second oxygen precursor, and an oxygen-containing plasma into the process chamber for a third number of cycles.
 18. The method of claim 14, further comprising performing an ultraviolet/oxygen treatment on the first dielectric layer.
 19. The method of claim 18, further comprising, after preforming the ultraviolet/oxygen treatment, performing a thermal treatment on the first dielectric layer.
 20. The method of claim 14, wherein the first silicon precursor and the second silicon precursor comprise a same chemical. 